D3071: Comparative morphology of antenna in the family Pleidae (Hemiptera: Heteroptera)

The family Pleidae, or pigmy backswimmers, have several morphological characteristics that are used to identify the species and help determine their evolutionary history. Besides using tarsal formulas to define each genus, another one of the main identifying characteristics in Pleidae is their antennal segments and sensilla. The antennae of the species in Pleidae exhibit about 12 types of sensilla and for the first time, all types of sensilla have been documented for this family. The family Pleidae contains four genera (Heteroplea, Paraplea, Plea, and Neoplea) and representatives of all the genera have been surveyed and their antennal sensilla have been documented. The antenna of Heteroplea shares characteristics with the family Helotrephidae, the sister to Pleidae, which suggests that its antennal type may be useful in determining relationships between species currently placed in these two families. However, there has been no phylogenetic analysis of this family and it is uncertain if the morphological characteristics are reliable characters for their classification. The antennae of N. striola and N. harnedi suggest that they are separate species and previous suggestions of synonymy are not supported. The purpose of this study is to document the sensilla found on the antennae of Pleidae and to look at the comparative morphology of the antennae.